Is neuro-ectodermal differentiation of Ewing's sarcoma of bone associated with an unfavourable prognosis?

Among Ewing's sarcoma (ES) of bone and related entities are tumours with neuro-ectodermal features that could represent a biologically distinct type. In order to assess the prognostic significance of the various forms of ES, a retrospective joint study involving three cancer centres in Europe and the U.S.A. was initiated. The material from 315 primary ES was reviewed by a panel of five pathologists and classified as typical ES (220 cases), atypical ES (48 cases) or ES with neuro-ectodermal features (47 cases). Prognostic factor analysis on treatment failurefree survival was performed using the Cox model. It included histopathological classification, initial patient characteristics, clinical presentation and treatment type. After multivariate analysis, in addition to treatment type ( P < 0.001), metastases ( P = 0.003) and proximal tumour location ( P = 0.006), two histopathological parameters correlated with poor treatment failure-free survival, the presence of filigree pattern ( P = 0.044) and dark cells ( P = 0.043). We conclude that ES with neuro-ectodermal features does not appear to have a different outcome to the other subtypes.